<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    body, ul{
      margin: 0;
      padding: 0;
    }

    body{
      background-image: url(../images/grid.png);
    }
    svg{
      background-color: rgba(255, 0, 0, 0.1);
    }
  </style>

</head>
<body>


  <svg width="300" height="300" xmlns="http://www.w3.org/2000/svg" >
    
    <!-- 1.ICON previous-->
    <symbol id="previous" viewBox="0 0 100 100">
      <path fill="currentColor" d="M 80 0,L 20 50, L 80 100 Z"></path>
    </symbol>

    <!-- 2.ICON next -->
    <symbol id="next" viewBox="0 0 100 100">
      <polygon points="20 0, 80 50, 20 100"></polygon>
    </symbol>

    <!-- 复用 -->
    <!-- <use href="#previous" width="100" height="100"></use> -->
  </svg>


  <!-- 复用 -->
  <svg width="300" height="300" xmlns="http://www.w3.org/2000/svg" >
    <!-- 直接在use上指定ICON的 width和 hegiht -->
    <use href="#previous" width="50" height="50"></use>
  </svg>

  <!-- 这个属于缩小 -->
  <svg width="30" height="30" xmlns="http://www.w3.org/2000/svg" >
    <use href="#previous" ></use>
  </svg>

  <!-- 属于放大 -->
  <svg width="200" height="200" xmlns="http://www.w3.org/2000/svg" >
    <use href="#previous" ></use>
  </svg>

</body>
</html>